Geology Reference
In-Depth Information
must be centrally involved in producing them. Eventually, he helped to make the discov-
ery that marine algae such as
Emiliania huxleyii
—the very same beings who contribute
so much to regulate Gaia's temperature by precipitating chalk—are major players in this
process.
It turns out that
Emiliania
, and indeed many other algae such as seaweeds, emit DMS
which finds its way into the atmosphere where it attracts the ardent attentions of oxygen.
Remember how oxygen, the passionate Italian of the chemical world, finds completion
by seducing electrons away from other atoms or molecules in order to complete its own
outer electron orbit. The gas DMS is a great target for oxygen's ardour, and when it has
sucked the electrons it needs from this larger molecular being, what remains, amongst
other things, are molecules of sulphate aerosol floating free in the air above the ocean.
These molecules have many special qualities, but one of critical importance for Earth's
climate is that water vapour finds them irresistibly attractive, preferring nothing better
than to condense around them in dense schools and shoals like so many fish swarming
around bread crumbs thrown into a lake.
The massive condensation triggered by molecules of sulphate aerosol derived from
DMS makes clouds that cool the Earth, because their dense white upper sur-
faces—familiar to anyone who has travelled by air—reflect solar energy back into
space. But can this astonishing relationship between algae and clouds help to regulate
the Earth's temperature by means of a negative feedback in which warmer oceans stim-
ulate algal growth, resulting in more DMS, more sulphate aerosol, more cloud condens-
ation nuclei and hence more planet-cooling clouds? This feedback, proposed by Love-
lock and his colleagues Robert Charlson, Stephen Warren and Meinrat Andreae, in its
simplest form looks like this
(Figure 27)
:
